1. Field of the Invention
This invention relates in general to electrical inductive apparatus, and more particularly to windings for such apparatus.
2. Description of the Prior Art
Electrical inductive apparatus, such as transformers and reactors, commonly utilize a high voltage winding which includes a plurality of electrically connected disc coils arranged in an axially aligned stack about a winding leg of a magnetic core. When an impulse voltage, such as caused by lightning or switching, is applied to the electrical inductive apparatus, a potential distribution along an axis of the winding thereof is determined by the distribution constant .alpha.. The distribution constant .alpha. is equal to the square root of the ratio of the capacitance Cg of the winding to ground to the series capacitance Cs of the winding. EQU .alpha.=.sqroot.Cg/Cs
The smaller the distribution constant .alpha., the more linear the potential distribution, due to the impulse voltage, will be across the axial direction of the winding, and the smaller the magnitude of the transient potential oscillation within the winding will be. Since the distribution constant .alpha. can be reduced by increasing the series capacitance Cs of the winding, various kinds of high voltage windings having increased series capacitance have been utilized. Interleaved windings are well known examles of such windings.
FIG. 1 shows one example of an interleaved winding. In FIG. 1 a conductor 1 through 10 and a conductor 11 through 20 are wound in parallel with each other on an insulating tube 102 via a ductrail 103 to form a pair of disc coils. The conductor 10 is connected to the conductor 11 at a point X so that the conductor 1 through 10 and the conductor 11 through 20 are connected in series with each other. The conductor 20 is also connected to a conductor 21 of a next pair of disc coils. Thus an interleaved winding 101 is made by connecting a plurality of the pairs of disc coils in series with each other, as is apparent to those skilled in the art. In the interleaved winding 101, the conductor 1 through 10 and the conductor 11 through 20 are wound in parallel with each other, thus being interleaved, and form a capacitor therebetween, the series capacitance of which becomes large. However in the interleaved winding 101, it is essential that two conductors be connected at one point X per pair of disc coils as shown in FIG. 1. It is also essential to wind the two conductors in parallel with each other in order to form a pair of disc coils.
In electrical inductive apparatus for large current use, an interleaved winding where a plurality of conductors are wound in parallel with each other in each of the disc coils is used. FIG. 2 shows an example of such an interleaved winding with a plurality of pairs of disc coils having three parallel conductors al through a72, b1 through b72, and c1 through c72. In making a pair of disc coils in the interleaved winding 101A shown in FIG. 2, two times three conductors namely six conductors, must be wound in parallel with each other. Also it is essential to connect three conductors at point X respectively per pair of disc coils (a6 to a7, b6 to b7, c6 to c7).
As described above, it is difficult and time consuming to make a conventional winding where many conductors are wound in parallel with each other in each of the disc coils.